This invention relates to design of telecommunications networks, and in particular to the protection of telecommunications networks against span failure.
For a few years now, those in industry have been increasingly expressing the desire for those in the research community to address the topic of hybrid (meaning integrated ring-mesh) survivable network design. Both of these basic networking technologies have their strengths and weaknesses. Mesh networks, with their high connectivity and common sparing, are capacity efficient and require minimal redundancy. However, they generally require more costly nodal equipment (DCS verses ADM""s), and they also require the line-level termination of all signals (working and spare) at every node. They tend, therefore, to be used for long haul architectures, where cost is more dependent on the total bandwidth-distance product. Rings, on the other hand, tend to be more cost efficient in metro areas, where cost is dominated by nodal equipment. Nodal equipment costs are much lower in rings, since they only terminate dropped traffic. However, there is much more redundancy required in the spare capacity of rings. A design methodology that leads to an optimized balance of the two, would not only guide current and future designs of hybrid networks, but would also reveal cost reduction opportunities in existing pure-ring or pure-mesh systems.
To date, the only clearly recognized principle for combined use of ring and mesh technology, has been that of access rings and a mesh core [2,3]. References in square brackets are listed at the end of the disclosure. In both these papers, rings or ring segments are used as sub-networks for metropolitan network access. This work considers the placement of rings over all parts of the mesh. In other words, this is a far more general approach than what has been previously done in this area.
There is therefore proposed in accordance with an aspect of the invention, a telecommunications network, in which the telecommunications network includes plural nodes interconnected by plural spans, each node having a nodal switching device (DCS or ADM) for making and breaking connections between adjacent spans at the node, all of the nodes of the network being arranged in a mesh network with integrated rings spread throughout the mesh network.
In a further aspect of the invention, there is proposed a method of creating a telecommunications network in which the telecommunications network includes plural nodes interconnected by plural spans, each node having a nodal switching device (DCS or ADM) for making and breaking connections between adjacent spans at the node, comprising the step of arranging the nodes of the network in a mesh network with integrated rings.
In a further aspect of the invention, there is proposed a method of creating a telecommunications network in which the telecommunications network includes plural nodes interconnected by plural spans, each node having a nodal switching device (DCS or ADM) for making and breaking connections between adjacent spans at the node, comprising the step of arranging the nodes of the network to avoid or reduce the deleterious effect of forcer spans.
In a further aspect of the invention, the telecommunications network is a mesh network having at least one forcer span and the method further comprises the steps of
integrating a ring into the mesh network; and
reducing the deleterious effect of the forcer span on the capacity design of the mesh network by integration of the ring into the mesh network.
Preferably, integrating a ring into the mesh network comprises the steps of
identifying a forcer span in the mesh network, and
placing a ring in the network that makes the forcer span a non-forcer span.
Further, preferably placing a ring in the network that makes the forcer span a non-forcer span comprises the step of:
evaluating plural ring placements based on the cost of placing each ring in the network.
Still further, a ring is selected for placement in the network that is the most cost effective of the ring placements evaluated. Integer programming or a heuristic may be used to evaluate the ring placements.